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A security guard closes the gate at the Pittsburgh Zoo, where zoo officials say a young boy was killed after he fell into the exhibit that was home to a pack of African painted dogs, who pounced on the boy and mauled him, Sunday, Nov. 4, 2012. It's not clear whether he died from the fall or the attack, said Barbara Baker, president and CEO of the Pittsburgh Zoo & PPG Aquarium. (AP Photo/John Heller) Photo by